Preparation of 4-azasaccharines

ABSTRACT

Compounds of formula I ##STR1## in which R is H, or an aliphatic or aromatic radical, R 1  is alkyl, R 2  is alkyl, alkoxy, aryl, aryloxy, aralkyl, alkaryl, aralkyloxy, alkaryloxy, alkaralkyl or alkaralkyloxy, and one of R 1  and R 2  is H and the other has the meaning given above. These compounds are intermediates for the preparation of herbicidal sulfonylureas.

This is a divisional of application Ser. No. 242,834 filed on Sept. 12,1988 now U.S. Pat. No. 4,889,933.

The invention relates to mono- or di-substituted 4-aza-saccharines, tomono- or di-substituted 4-aza-dihydro- or -tetrahydro-saccharines asintermediates and to processes for the preparation thereof.

R. F. Sauers et al. describe herbicides based on sulfonylureas in ACSSymposium Series 255, pages 21-28, (1984). Herbicidally activepyridylsulfonyl ureas are described, for example, in EP-A-0 013 480,EP-A-0 084 224, EP-A-0 097 122, EP-A-0 126 711 and EP-A-0 139 612. Themulti-stage processes for the preparation thereof are uneconomical andthe starting materials are difficult to obtain.

EP-A-0 172 140 describes the preparation of pyridine-2,3-dicarboxylicacids by the Diels-Alder reaction of 1-azadienes withethylene-1,2-dicarboxylic acid derivatives to form1-aminotetrahydropyridine-2,3-dicarboxylic acid derivatives, removal ofthe amino group and subsequent oxidation of the resulting1,4-dihydropyridines.

The invention relates to compounds of formula I ##STR2## in which R isH, linear or branched C₁ -C₂₀ alkyl, C₂ -C₂₀ alkenyl or C₂ -C₂₀ alkynyl,C₃ -C₁₀ cycloalkyl, C₄ -C₂₀ cycloalkylalkyl, C₄ -C₂₀ alkylcycloalkyl, C₅-C₂₀ alkylcycloalkylalkyl, C₆ -C₁₄ aryl, C₇ -C₂₀ -aralkyl or -alkaryl orC₈ -C₂₀ alkaralkyl, each of which is unsubstituted or substituted by--OH, --CN, halogen, C₁ -C₁₂ -alkoxy or -alkylthio, C₆ -C₁₀ aryl-oxy or-thio, C₇ -C₁₆ -aralkyloxy, -alkaryloxy, -aralkylthio or -alkarylthio,C₈ -C₁₈ alkaralkyloxy or -thio, --NR³ R⁴, --COOR⁵, --OCOR⁶, --CONR³ R⁴or by --NR³ COR⁶, in which each of R³ and R⁴, independently of theother, is C₁ -C₁₂ alkyl, C₅ - or C₆ -cycloalkyl, C₆ -C₁₀ aryl, C₇ -C₁₆aralkyl or C₈ -C₁₆ alkaralkyl or R³ and R⁴ together are tetra- orpenta-methylene or 3-oxapentylene, R⁵ is H, C₁ -C₁₂ alkyl, phenyl,benzyl, cyclohexyl or cyclopentyl and R⁶ is C₁ -C₁₂ acyl,

R¹ is H, or linear or branched C₁ -C₁₂ alkyl which is unsubstituted orsubstituted by hydroxy, halogen, cyano, C₁ -C₄ alkoxy, carboxy, C₁ -C₁₂acyloxy or by C₁ -C₄ alkoxycarbonyl, R² is H, or C₁ -C₁₂ -alkyl or-alkoxy, C₆ -C₁₀ -aryl or -aryloxy, C₇ -C₁₆ -aralkyl, -alkaryl,-alkaryloxy or -aralkyloxy, or C₈ -C₁₆ alkaralkyloxy, which areunsubstituted or substituted by hydroxy, halogen, cyano, C₁ -C₄ alkoxy,carboxy, C₁ -C₁₂ acyloxy or by C₁ -C₄ alkoxycarbonyl.

R as alkyl contains preferably from 1 to 12, especially from 1 to 8,carbon atoms. In a preferred sub-group, R is α,α-branched alkyl havingespecially from 4 to 12 carbon atoms. Examples of alkyl are methyl,ethyl, n- and iso-propyl, n-, iso- and tert.-butyl,1,1-dimethylprop-1-yl, pent-1-, -2- or -3-yl, 1,1-, 1,2-, 1,3- or2,2-dimethylprop-1-yl, 1,2,2-trimethylprop-1-yl, 1-, 2- or 3-hexyl,1,1-, 1,2-, 1,3-, 1,4-, 2,3- or 3,4-dimethylbut-1-yl,1,1,2,2-tetramethylethyl, 1-, 2-, 3- or 4-heptyl, 1,1-dimethylhex-1-yl,2-methylhept-2-yl, 3-methylhept-3-yl, 1,1,2,2-tetramethylprop-1-yl, 1-,2-, 3- or 4-octyl, 2-ethyloct-1-yl, 1,1,3,3-tetramethylbut-1-yl,1-methylhept-1-yl, 4-methylhept-1-yl, and also nonyl, decyl, undecyl,dodecyl, tetradecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl,eicosyl and their isomers.

R as alkenyl and alkynyl contains preferably from 2 to 12, especiallyfrom 2 to 10, carbon atoms. These radicals correspond especially to theformulae C₂ -C₆ alkenyl-C_(n) H_(2n) - and C₂ -C₆ alkynyl-C_(n) H_(2n) -in which n is preferably 1, 2 or 3. Examples are vinyl, allyl, crotonyl,but-2- or but-3-en-1-yl, but-1-en-1-yl, but-1-en-3-yl, pent-1-, -2- or-3-en-5-yl, 1,1-dimethylprop-2-en-1-yl, but-2-en-4-yl, hex-1-, -2-, -3-or -4-en-6-yl, hex-2-, -3- or -4-en-6-yl, hex-2-en-4-yl, hex-3-en-5- or-6-yl, hept-1-en-3-, -4-, -5-, -6- or -7-yl, hept-3-en-5- or -6-yl,oct-1-, -2-, -3-, -4-, -5- or -6-en-8-yl, oct-2-en-4-yl, non-7-en-9-yl,dec-8-en-10-yl and corresponding alkyne radicals. Allyl and propargylare preferred.

R as cycloalkyl contains preferably from 4 to 8, especially 5 or 6,carbon atoms. Examples are cyclopropyl, cyclobutyl, cycloheptyl,cyclooctyl, cyclononyl, cyclodecyl and, especially, cyclopentyl orcyclohexyl.

R as cycloalkylalkyl contains preferably from 4 to 12 carbon atoms andis especially C₄ -C₈ cycloalkyl-C_(n) H_(2n) - in which n is 1, 2 or 3.The cycloalkyl is preferably cyclopentyl and cyclohexyl. Examples arecyclopentylmethyl, 1- or 2-cyclopentyleth-1- or -2-yl, cyclohexylmethyl,1- or 2-cyclohexyleth-1-or -2-yl and 1-, 2- or 3-cyclohexylprop-1- or-2-yl.

R as alkylcycloalkyl contains preferably from 4 to 12 carbon atoms andis especially C₁ -C₉ alkyl-C₄ -C₈ cycloalkyl. The cycloalkyl isespecially cyclopentyl or cyclohexyl. Examples are methyl- ordimethyl-cyclopentyl, ethylcyclopentyl, methyl- or dimethyl-cyclohexyl,ethyl- or propyl- or butyl-cyclohexyl and methylethylcyclohexyl.

R as alkylcycloalkylalkyl contains preferably from 5 to 12 carbon atomsand is especially C₁ -C₄ alkyl-C₄ -C₈ cycloalkyl-C_(n) H_(2n) - in whichn is 1, 2 or 3. The cycloalkyl is preferably cyclopentyl or cyclohexyl.Examples are methylcyclohexylmethyl and 1- or2-(methylcyclohexyl)-eth-1- or -2-yl.

R as aryl contains preferably from 6 to 10 carbon atoms. Examples arephenanthryl, naphthyl and, especially, phenyl.

R as aralkyl contains preferably from 7 to 16, especially from 7 to 12,carbon atoms. The aryl is preferably phenyl. The aralkyl correspondspreferably to the formula phenyl-C_(n) H_(2n) - in which n is 1, 2 or 3.Examples are benzyl, 1- or 2-phenyleth-1- or -2-yl and 1- or2-phenylprop-1-, -2- or -3-yl.

R as alkaryl contains preferably from 7 to 16 carbon atoms. The aryl ispreferably phenyl. R corresponds especially to C₁ -C₁₀ alkylphenyl.Examples are methylphenyl, dimethylphenyl, ethylphenyl,methylethylphenyl, n- or iso-propylphenyl, butylphenyl, hexylphenyl,octylphenyl, nonylphenyl and decylphenyl.

As alkaralkyl, R contains preferably from 7 to 16 carbon atoms. The arylis preferably phenyl. As alkaralkyl, R is especially C₁ -C₁₆alkylphenyl-C_(n) H_(2n) -in which n is 1, 2 or 3. Examples aremethylbenzyl, ethylbenzyl, n- or iso-propylbenzyl, butylbenzyl,dimethylbenzyl, octylbenzyl, nonylbenzyl, (methylphenyl)eth-1- or -2-yland (methylphenyl)prop-1-, -2- or -3-yl.

In a preferred embodiment, R is H or unsubstituted or substituted C₁-C₁₂ alkyl, C₆ -C₁₀ aryl, C₇ -C₁₆ -aralkyl or alkaryl, or C₈ -C₁₆alkaralkyl, the aryl being especially phenyl. In an especially preferredembodiment, R is H or unsubstituted or substituted C₁ -C₈ alkyl, phenyl,phenyl-C₁ -C₃ alkyl, C₁ -C₄ alkylphenyl or C₁ -C₄ alkylphenyl-C₁ -C₃alkyl.

The radical R may be mono- or poly-substituted, preferably mono- totri-substituted. The substituents may be:

--OH, --CN, halogen, preferably Br, Cl, F;

C₁ -C₁₂ -, preferably C₁ -C₄ -alkoxy and -alkylthio, for examplemethoxy, ethoxy, n- or iso-propoxy, butoxy, methylthio, ethylthio;

C₆ -C₁₀ aryl-oxy and -thio, especially phenoxy or phenylthio;

C₇ -C₁₆ -, preferably C₇ -C₁₂ -alkaryl-oxy or -thio; the aryl radicalpreferably being a phenyl radical, for example methyl-, dimethyl-,ethyl-, methylethyl-, n- or iso-propyl-, butyl-, octyl- anddecyl-phenyl-oxy or -thio;

C₇ -C₁₆ -, preferably C₇ -C₁₀ -aralkyl-oxy and -thio, the aryl radicalpreferably being a phenyl radical, for example benzyloxy, benzylthio,phenylethoxy;

C₈ -C₁₆ -, preferably C₈ -C₁₂ -alkaralkyl-oxy and -thio, the arylradical preferably being a phenyl radical, for example methylbenzyloxy,ethylbenzyloxy, (methylphenyl)ethoxy, methylbenzylthio; --NR³ R⁴,--CONR³ R⁴ and --NR³ COR⁶ in which each of R³ and R⁴, independently ofthe other, is preferably C₁ -C₄ alkyl, cyclopentyl, cyclohexyl, phenylor benzyl and R⁶ is preferably C₁ -C₈ acyl. Examples of acyl are formyl,acetyl, propionyl, butanoyl, hexanoyl, benzoyl, chloroacetyl,dichloroacetyl, fluoroacetyl, trichloroacetyl and trifluoroacetyl;--COOR⁵ and --OCOR⁶ in which R⁵ is preferably H or C₁ -C₄ alkyl and R⁶has the preferred meanings given above.

The substituents alkoxy, alkylthio, aryloxy, arylthio, alkaryl-oxy and-thio, aralkyl-oxy and -thio and alkaralkyl-oxy and -thio may themselvesbe substituted, for example by --OH, --CN, F, Cl, C₁ -C₄ alkoxy, --NR³R⁴, --COOR⁵, --OCOR⁶, --CONR³ R⁴ or by --NR³ COR⁶, R³ to R⁶ having themeanings and preferred meanings given above. Examples of suchsubstituents are β-chloroethoxy, β-cyanoethoxy, chlorophenoxy,dichlorophenoxy, fluorophenoxy, trifluorophenoxy,chlorotrifluoromethylphenoxy, cyanophenyl, chlorobenzyloxy,(methoxycarbonyl)-ethoxy or -methoxy, acetoxy-ethoxy or -methoxy anddimethylaminocarbonylphenoxy.

R¹ as alkyl contains preferably from 1 to 8, especially from 1 to 4,carbon atoms. Preferred examples are methyl, ethyl and n- andiso-propyl. In a preferred embodiment, R¹ is H. Preferred substituentsof R¹ are hydroxy, cyano, F, Cl, carboxy and C₁ -C₄ alkoxy.

R² as alkyl and alkoxy contains preferably from 1 to 6 carbon atoms andis, for example, methyl, ethyl, n- and iso-propyl, n- and iso-butyl,pentyl, hexyl, methoxy, ethoxy, n- and iso-propoxy and n- andiso-butoxy. As aryl, R² is especially phenyl and, as aryloxy, especiallyphenoxy. R² as aralkyl or aralkyloxy is preferably phenyl-C_(n) H_(2n)--(O--)m in which n is 1, 2 or 3 and m is 0 or 1; benzyl and benzyloxyare preferred. R² as alkaryl or alkaryloxy is preferably C₁ -C₄alkyl-phenyl or -phenoxy, for example methylphenyl, dimethylphenyl andmethylphenoxy. R² as alkaralkyl or alkaralkyloxy is preferably C₁ -C₄alkyl-benzyl or -benzyloxy, for example methylbenzyl or methylbenzyloxy.

In a preferred sub-group, R² is unsubstituted or substituted C₁ -C₆-alkyl or -alkoxy, phenyl, phenyloxy, benzyl, benzyloxy, C₁ -C₄-alkylphenyl or -alkylphenoxy or C₁ -C₄ -alkyl-benzyl or -benzyloxy.

The compounds of formula I that are preferred are those in which R is H,α,α-branched C₄ -C₁₂ alkyl, or unsubstituted or methoxy-, nitro- orhalo-substituted benzyl, R¹ is H or C₁ -C₄ alkyl and R² is H, C₁ -C₄alkyl or C₁ -C₄ alkoxy. Of these preferred compounds of formula I thecompounds that are, again, especially preferred are those in which R isH or α,α-branched C₄ -C₈ alkyl and especially those in which R is H.

The compounds of formula I can be prepared analogously to the processdescribed in EP-A-0 172 140, in which process an azadiene of formula II##STR3## in which each of R⁷ and R⁸, independently of the other, has thesame meanings as R³ and R⁴, is reacted with a compound of formula III##STR4## in which R° has the same meaning as R, with the exception of H,to form a compound of formula IV ##STR5## the compound of formula IV isconverted into a compound of formula V ##STR6## by treatment with anacid and/or by thermal treatment with removal of R⁷ R⁸ NH, the compoundof formula V is oxidised to a compound of formula I, and, for thepreparation of compounds of formula I in which R is H, the compound offormula V is reacted with a strong acid.

The process conditions are described in detail in EP-A-0 172 140.

For the removal of the group R° for the preparation of compounds offormula I in which R is H, there are used preferably halogenatedaliphatic C₂ -C₄ carboxylic acids, for example difluoro- ortrifluoroacetic acid, α,α-difluoropropionic acid, perfluoropropionicacid or 1,1,1-trifluoro-2,2-dichloropropionic acid.

The unsaturated hydrazones of formula II are known or can be prepared byreacting α,β-unsaturated aldehydes with N,N-substituted hydrazines. Thecompounds of formula III are described, for example, in J. of Heteroc.Chem., 8, 571 and 591 (1971) and can be prepared analogously to theprocesses described therein.

The invention also relates to the compounds of formulae IV and V inwhich R° has the same meaning as R, with the exception of H. R, R¹ andR² have the preferred meanings given in the case of the compound offormula I.

It has been found that certain compounds of formula I are obtaineddirectly when R° in formula III is an α,α-branched aliphatic radical andthe reaction is carried out in an organic sulfoxide as solvent.

The invention also relates to a process for the preparation of compoundsof formula Ia ##STR7## in which R¹ and R² have the meanings given aboveand R⁹ is α,α-branched C₄ -C₂₀ alkyl, C₅ -C₂₀ -alkenyl or -alkynyl,1-(C₁ -C₄ alkyl)-C₃ -C₁₀ cycloalk-1-yl, α,α-branched C₆ -C₂₀cycloalkylalkyl, C₇ -C₂₀ alkylcycloalkylalkyl, C₉ -C₁₆ aralkyl or C₁₀-C₁₆ alkaralkyl, which process comprises reacting a compound of formulaII ##STR8## in which each of R⁷ and R⁸, independently of the other, hasthe same meanings as R³ and R⁴, with a compound of formula IIIa ##STR9##in which R⁹ has the meaning given above, in the presence of oxygen andan organic sulfoxide as solvent, at elevated temperature and withremoval of R⁷ R⁸ NH.

R⁹ may be substituted as defined for R in formula I. R⁹ is especiallyα,α-branched C₄ -C₁₂ alkyl. R⁹ as α,α-branched alkenyl or alkynylcontains preferably from 5 to 10 carbon atoms. R⁹ as 1-(C₁ -C₄alkyl)cycloalk-1-yl contains preferably from 4 to 8, especially 5 or 6,carbon atoms in the cycloalkyl radical. R⁹ as α,α-branchedcycloalkylalkyl is preferably C₄ -C₈ -, especially C₅ - or C₆-cycloalkyl-C₃ -C₈ alkyl. R⁹ as α,α-branched alkylcycloalkylalkyl ispreferably C₁ -C₄ alkyl-C₄ -C₈ -, especially -C₅ - or -C₆ -cycloalkyl-C₃-C₈ -, especially -C₃ -C₆ -alkyl. R⁹ as α,α-branched aralkyl containsespecially from 9 to 14 carbon atoms and is especially phenyl-C₃ -C₆alkyl. As alkaralkyl, R⁹ is preferably C₁ -C₄ alkylphenyl-C.sub. 3 -C₆alkyl. Examples are tert.-butyl, 1,1-dimethyl-but-1-yl or -prop-1-yl,2-methyl-but-2-yl, 1,1,3,3-tetramethylprop-1-yl,1,1,2,2-tetra-methylethyl, 1,1-dimethyl-pent-1-yl or -hex-1-yl,1-methylcyclohex-1-yl, 2-cyclopentylprop-2-yl,2-(methylcyclohexyl)prop-2-yl, 2-phenylprop-2-yl and2-(methylphenyl)prop-2-yl.

Suitable sulfoxides are, for example, diethyl sulfoxide, methyl ethylsulfoxide, tetramethylene or pentamethylene sulfoxide and, especially,dimethyl sulfoxide.

The reaction temperature is preferably from 50° to 200° C., especiallyfrom 60° to 150° C. The reaction can be carried out in a pure oxygenatmosphere or in oxygen/inert gas mixtures, for example air.

It has also been found that, when using an organic sulfoxide as solvent,compounds of formula I are obtained in a two-stage process, the pyridinering being formed in the first stage with removal of R⁷ R⁸ NH.

The invention also relates to a process for the preparation of compoundsof formula Ib ##STR10## in which R¹ and R² have the meanings given aboveand R¹⁰ has the same meaning as R but is not H and does not have thesame meaning as R⁹, which process comprises reacting a compound offormula II ##STR11## in which each of R⁷ and R⁸, independently of theother, has the same meanings as R³ and R⁴, in the presence of oxygen andan organic sulfoxide as solvent at elevated temperatures, with acompound of formula IIIb ##STR12## to form a compound of formula VI##STR13## and the compound VI is cyclised to a compound of formula Ibwith removal of R⁷ R⁸ NH.

R¹⁰ has the same preferred meanings as given for R in formula I and thereaction conditions are those preferred for the previously describedprocess.

The cyclisation is preferably carried out with strong acids, for exampleconcentrated sulfuric acid. Glacial acetic acid is advantageously usedas solvent.

The isolation of the compounds of formulae I, Ia, Ib, IV, V and VI canbe carried out in customary manner, for example by evaporating off thesolvent and by filtration, sublimation or distillation. The compoundscan be further purified by recrystallisation or by chromatographicmethods.

The compounds of formula I are valuable intermediates, for example forthe preparation of sulfonylureas that can be used as herbicides (see R.F. Sauers et al., ACS Symposium Series 255, pages 21-28 (1984)).

The following Examples illustrate the invention in more detail.Percentages are percentages by weight unless otherwise indicated. Thenomenclature is based on the following structural formula of the4-azasaccharine: ##STR14##

PREPARATION EXAMPLES Example 1

18.9 g of 2-ethyl-4-dimethylamino-4-azabutadiene and 12.6 g of2-tert.-butylisothiazolin-3-one-1,1-dioxide are heated under reflux in200 ml of ethanol for 8 hours. After concentration by evaporation, theresidue is recrystallised from ether/petroleum ether to give 25 g (79%of the theoretical yield) of crystalline compound of formula IVa##STR15##

Example 2

(a) 6.4 g of 2-methoxyacrolein are stirred for 1 hour at 30°-35° C. with4.4 g of N,N-dimethylhydrazine in 50 ml of ether, dried at 20° C. withNa₂ SO₄ and then the solvent is removed. Distillation at 74°-76° C./13mbar gives 6.2 g of pure 2-methoxy-4-dimethylamino-4-azabutadiene.

(b) 10.8 g of 2-methoxy-4-dimethylamino-4-azabutadiene and 15 g of2-tert.-butylisothiazolin-3-one-1,1-dioxide are stirred for 11/2 h at80°-85° C. in 250 ml of toluene. The crude bicyclic compound of formulaIVb is further processed in the crude state as described in Example 4.##STR16## The compounds listed in Table 1 are obtained in an analogousmanner.

                                      TABLE 1                                     __________________________________________________________________________     ##STR17##                                                                    No.                                                                              R.sub.1                                                                          R.sub.2     R            m.p.                                           __________________________________________________________________________    01.01                                                                            H  CH.sub.2 CH.sub.3                                                                         tert.-butyl  90°-92° C.                       01.02                                                                            CH.sub.3                                                                         CH.sub.3    tert.-butyl  50°-52° C.                       01.03                                                                            H  CH.sub.3    tert.-butyl                                                 01.04                                                                            H  CH.sub.2 CH.sub.3                                                                         C(CH.sub.3).sub.2CH.sub.2 C(CH.sub.3).sub.3                 01.05                                                                            H  OCH.sub.3   tert.-butyl                                                 01.06                                                                            H                                                                                 ##STR18##  tert.-butyl                                                 01.07                                                                            H  OCH.sub.2 CH.sub.3                                                                        tert.-butyl                                                 01.08                                                                            CH.sub.3                                                                         H           tert.-butyl                                                 01.09                                                                            CH.sub.3                                                                         OCH.sub.3   tert.-butyl                                                 01.10                                                                            H  OCH.sub.3                                                                                  ##STR19##                                                  01.11                                                                            H  CH.sub.2 OCH.sub. 3                                                                       tert.-butyl                                                 01.12                                                                            H  SCH.sub.3   tert.-butyl                                                 01.13                                                                            H  CH(CH.sub.3).sub.2                                                                        tert.-butyl                                                 __________________________________________________________________________

Example 3

25 g of cyclo-adduct of the structure according to Example 1 and 55 g ofsilica gel are heated for 75 minutes at 100° C. in 300 ml of toluene.After removing the silica gel by filtration and rinsing, the yellowsolution is concentrated by evaporation and the residue is digested withpetroleum ether to give 15.5 g (73%) of yellow powder which isrecrystallised from CCl₄. Cyclo-adducts substituted in different mannersare reacted in an analogous manner. There is obtained ##STR20##

Example 4

9 g of trifluoroacetic acid are added at room temperature to thecyclo-adduct according to Example 2 and the batch is then stirred for 1hour. The crude bicyclic compound of formula Va is further processed asdescribed in Example 6.

The compounds listed in Table 2 are obtained in an analogous manner.

                                      TABLE 2                                     __________________________________________________________________________     ##STR21##                                                                    No.                                                                              R.sup.1                                                                          R.sup.2     R           m.p.                                            __________________________________________________________________________    02.01                                                                            H  CH.sub.2 CH.sub.3                                                                         tert.-butyl 161°-163° C.                      02.02                                                                            CH.sub.3                                                                         CH.sub.3    tert.-butyl 133°-136° C.                      02.03                                                                            H  CH.sub.3    tert.-butyl 178°-179° C.                      02.04                                                                            H  CH.sub.2 CH.sub.3                                                                         C(CH.sub.3).sub.2 CH.sub.2 C(CH.sub.3).sub.3                                              109°-113° C.                      02.05                                                                            H  OCH.sub.3   tert.-butyl                                                 02.06                                                                            H                                                                                 ##STR22##  tert.-butyl                                                 02.07                                                                            H  OCH.sub.2 CH.sub.3                                                                        tert.-butyl                                                 02.08                                                                            CH.sub.3                                                                         H           tert.-butyl                                                 02.09                                                                            CH.sub.3                                                                         OCH.sub.3   tert.-butyl                                                 02.10                                                                            H  OCH.sub.3                                                                                  ##STR23##                                                  02.11                                                                            H  CH.sub.2 OCH.sub.3                                                                        tert.-butyl                                                 02.12                                                                            H  SCH.sub.3   tert.-butyl                                                 02.13                                                                            H  CH(CH.sub.3).sub.2                                                                        tert.-butyl                                                 __________________________________________________________________________

Example 5

14.1 g of compound having the structure given in Example 3 are heated to65° C. in 130 ml of glacial acetic acid, and 6.4 g of pyrolusite areadded. After one hour at 60° C. the batch is filtered and the filtrateis concentrated by evaporation. The residue is partitioned between waterand chloroform. The organic phase is washed twice with water, dried andconcentrated by evaporation. The light beige residue is digested withpetroleum ether. 13 g (93%) of 6-ethyl-N-tert.-butyl-4-azasaccharine areobtained.

Example 6

Equimolar amounts of 2-methyl-4-dimethylamino-4-azabutadiene and2-tert.-butylisothiazolin-3-one-2,2-dioxide are heated at from 80° to90° C. in dimethyl sulfoxide. After one hour the batch is heated to aninternal temperature of 100° C. After an induction phase, the reactionbecomes exothermic. The heating bath is removed and cooling is effectedwith a water bath. Stirring is effected for 30 minutes at 100° C. andthen the solvent is removed by distillation under a high vacuum and theresidue is recrystallised from CCl₄ to give a 40% yield of6-methyl-N-tert.-butyl-4-azasaccharine.

Example 7

12.6 g of bromine are added at room temperature to the cyclo-adductaccording to Example 4. 24 g of triethylamine are then added dropwiseand the batch is stirred for 15 hours at from 20°-25° C. The suspensionis concentrated completely by evaporation, water and ethyl acetate areadded and the organic phase is separated off. The latter is concentratedcompletely by evaporation and the residue is recrystallised fromethanol, thus giving the compound of formula Ic which has a meltingpoint of 216°-217° C. ##STR24##

                                      TABLE 3                                     __________________________________________________________________________    No.                                                                              R.sup.1                                                                          R.sup.2     R           m.p.                                            __________________________________________________________________________    03.01                                                                            H  CH.sub.2 CH.sub.3                                                                         tert.-butyl 149°-151° C.                      03.02                                                                            CH.sub.3                                                                         CH.sub.3    tert.-butyl 150°-152° C.                      03.03                                                                            H  CH.sub.3    tert.-butyl 170°-172° C.                      03.04                                                                            H  CH.sub.3    C(CH.sub.3).sub.2 CH.sub.2 C(CH.sub.3).sub.3                                              221°-222° C.                      03.05                                                                            H  OCH.sub.3   tert.-butyl 216°-217° C.                      03.06                                                                            H                                                                                 ##STR25##  tert.-butyl                                                 03.07                                                                            H  OCH.sub.2 CH.sub.3                                                                        tert.-butyl                                                 03.08                                                                            CH.sub.3                                                                         H           tert.-butyl                                                 03.09                                                                            CH.sub.3                                                                         OCH.sub.3   tert.-butyl                                                 03.10                                                                            H  OCH.sub.3                                                                                  ##STR26##                                                  03.11                                                                            H  CH.sub.2 OCH.sub.3                                                                        tert.-butyl                                                 03.12                                                                            H  SCH.sub.3   tert.-butyl                                                 03.13                                                                            H  CH(CH.sub.3).sub.2                                                                        tert.-butyl 123°-125° C.                      __________________________________________________________________________

Example 8

11.5 g of compound according to Example 7 are heated at 120° C. in 42 mlof trifluoroacetic acid. After 3 hours, the batch is concentrated byevaporation and the residue is digested with ethyl acetate/diethylether. The powder is isolated by filtration and dried in vacuo to give6-ethylazasaccharine in a yield of 60% and with a melting point of199°-201° C.

                  TABLE 4                                                         ______________________________________                                         ##STR27##                                                                    No.     R.sup.1 R.sup.2          m.p.                                         ______________________________________                                        04.01   H       CH.sub.2 CH.sub.3                                                                              199°-201° C.                   04.02   CH.sub.3                                                                              CH.sub.3         267°-270° C.                   04.03   H       CH.sub.3         215°-217° C.                   04.04   H       OCH.sub.3        255°-256° C.                   04.05   H                                                                                      ##STR28##                                                    04.06   H       OCH.sub.2 CH.sub.3                                            04.07   CH.sub.3                                                                              H                                                             04.08   CH.sub.3                                                                              OCH.sub.3                                                     04.09   H       CH.sub.2 OCH.sub.3                                            04.10   H       CH(CH.sub.3).sub.2                                                                             199°-202° C.                   ______________________________________                                    

Example 9

The procedure is the same as in Example 6 and2-methyl-4-dimethylamino-4-azabutadiene is reacted with an isothiazolinewhich has been substituted at the N atom by benzyl or p-methoxybenzyl.There is obtained

    ______________________________________                                         ##STR29##                                                                    Example                        melting point                                                                          yield                                 no.    R.sup.1                                                                             R.sup.2                                                                              R          (°C.)                                                                           (%)                                   ______________________________________                                        10     H     CH.sub.3                                                                             benzyl     169-170  43                                    11     H     CH.sub.3                                                                             p-methoxybenzyl                                                                          141-143  42                                    ______________________________________                                    

Example 12

5.0 g of compound according to Example 10 are heated for 20 hours at100° C. in 30 ml of glacial acetic acid and 0.75 g of concentratedsulfuric acid. The reaction mixture is concentrated by evaporation, theresidue is dissolved in chloroform and washed with 1N NaHCO₃ solution.The organic phase is dried over MgSO₄ and then concentrated byevaporation. Digestion is then effected with diethyl ether to give 3.9 g(90%) of 6-methyl-N-benzyl-4-azasaccharine in the form of beige crystalshaving a melting point of 167°-170° C.

Application Example (a) Preparation of a sulfonylurea

1 mol of 6-methyl-4-azasaccharine is suspended in 10 times the volume ofmethanol and heated at 100° C. with 1/10 molar equivalent ofconcentrated sulfuric acid in a bomb tube. After 18 hours the batch isconcentrated by evaporation and the residue is washed with CHCl₃ /NaHCO₃to give 3-(aminosulfonyl)-5-methylpyridine-2-carboxylic acid methylester in the form of a beige powder having a melting point of 86°-88° C.

1 mol of the ester is dissolved in acetonitrile, and a solution of5-methyl-3-methoxy-1-(phenoxycarbonylamino)triazine in acetonitrile isadded dropwise thereto over a period of 75 minutes. After stirring forone hour, the batch is concentrated by evaporation, the residue is takenup in water, and 1 molar equivalent of 1N HCl is added dropwise. Theprecipitate is isolated by filtration and dried to give ##STR30## whichhas a melting point of 168°-170° C.

(b) Demonstration of herbicidal action in pre-emergence application

In a greenhouse, plant seeds of dicotyledonous and monocotyledonousweeds are sown in pots 11 cm in diameter. Immediately afterwards, thesurface of the soil is treated with an aqueous dispersion or solution ofthe test compounds. Concentrations of 0.5, 0.125 and 0.03 kg of testcompound per hectare are used. The pots are then kept in the greenhouseat a temperature of 22°-25° C. and 50-70% relative humidity. After 3weeks the test is evaluated and the action is assessed in accordancewith the following scale of ratings:

1 plant has not germinated or has withered.

2-3 very pronounced action.

4-6 medium action.

7-8 weak action.

9 no action (as untreated control).

    ______________________________________                                        Test results (pre-emergent)                                                              action application rate                                                       kg/ha                                                              Test plant   0,500       0,125  0,03                                          ______________________________________                                        Alopecurus myos.                                                                           3           4      5                                             Echinochloa c.g.                                                                           2           3      7                                             Amaranthus ret.                                                                            2           2      3                                             Chenopodium Sp.                                                                            3           4      7                                             Sinapsis     2           2      2                                             Stellaria    3           4      4                                             Chrysanth. leuc.                                                                           2           2      3                                             Galium aparine                                                                             2           3      5                                             Viola tricolor                                                                             2           2      2                                             Veronica Sp. 2           3      3                                             ______________________________________                                    

What is claimed is:
 1. A process for the preparation of a compound offormula I ##STR31## in which R is H, linear or branched C₁ -C₂₀ alkyl,C₂ -C₂₀ alkenyl or C₂ -C₂₀ alkynyl, C₃ -C₁₀ cycloalkyl, C₄ -C₂₀cycloalkylalkyl, C₄ -C₂₀ alkylcycloalkyl, C₅ -C₂₀ alkylcycloalkylalkyl,C₆ -C₁₄ aryl, C₇ -C₂₀ -aralkyl or -alkaryl or C₈ -C₂₀ -alkaralkyl, eachof which is unsubstituted or substituted by --OH, --CN, halogen, C₁ -C₁₂-alkoxy or -alkylthio, C₆ -C₁₀ aryl-oxy or -thio, C₇ -C₁₆ -aralkyloxy,-alkaryloxy, -aralkylthio or -alkarylthio, C₈ -C₁₈ alkaralkyloxy or-thio, --NR³ R⁴, --COOR⁵, --OCOR⁶, --CONR³ R⁴ or by --NR³ COR⁶, in whicheach ofR³ and R⁴, independently of the other, is C₁ -C₁₂ alkyl, C₅ - orC₆ -cycloalkyl, C₆ -C₁₀ aryl, C₇ -C₁₆ aralkyl or C₈ -C₁₆ alkaralkyl orR³ and R⁴ together are tetra- or penta-methylene or 3-oxapentylene, R⁵is H, C₁ -C₁₂ alkyl, phenyl, benzyl, cyclohexyl or cyclopentyl and R⁶ isC₁ -C₁₂ acyl, R¹ is H, or linear or branched C₁ -C₁₂ alkyl which isunsubstituted or substituted by hydroxy, halogen, cyano, C₁ -C₄ alkoxy,carboxy, C₁ -C₁₂ acyloxy or by C₁ -C₄ alkoxycarbonyl, R² is H, or C₁-C₁₂ -alkyl or -alkoxy, C₆ -C₁₀ -aryl or -aryloxy, C₇ -C₁₆ -aralkyl,-alkaryl, -alkaryloxy or -aralkyloxy, or C₈ -C₁₆ alkaralkyloxy, whichare unsubstituted or substituted by hydroxy, halogen, cyano, C₁ -C₄alkoxy, carboxy, C₁ -C₁₂ acyloxy or by C₁ -C₄ alkoxycarbonyl,in which anazadiene of formula II ##STR32## in which each of R⁷ and R⁸,independently of the other, has the same meanings as R³ and R⁴, isreacted with a compound of formula III ##STR33## in which R° has thesame meaning as R, with the exception of H, to form a compound offormula IV ##STR34## the compound of formula IV is converted into acompound of formula V ##STR35## by treatment with an acid and/or bythermal treatment with removal of R⁷ R⁸ NH, the compound of formula V isoxidized to a compound of formula I, and, for the preparation ofcompounds of formula I in which R is H, the compound of formula V isreacted with a strong acid.
 2. A process according to claim 1, which iscarried out at a temperature of from 50° to 200°.